Create Lua frontend GUI code

.luacheckrc

@@ -19,7 +19,14 @@ read_globals = {
 	"Settings",
 
 	string = {fields = {"split", "trim"}},
-	table  = {fields = {"copy", "getn", "indexof", "insert_all"}},
+	table  = {fields = {
+		"copy",
+		"shallow_copy",
+		"getn",
+		"indexof",
+		"insert_all",
+		"merge"
+	}},
 	math   = {fields = {"hypot", "round"}},
 }
 

builtin/common/misc_helpers.lua

@@ -489,6 +489,15 @@ function table.copy(t, seen)
 end
 
 
+function table.shallow_copy(t)
+	local new = {}
+	for k, v in pairs(t) do
+		new[k] = v
+	end
+	return new
+end
+
+
 function table.insert_all(t, other)
 	for i=1, #other do
 		t[#t + 1] = other[i]
@@ -497,6 +506,15 @@ function table.insert_all(t, other)
 end
 
 
+function table.merge(...)
+	local new = {}
+	for _, t in ipairs{...} do
+		table.insert_all(new, t)
+	end
+	return new
+end
+
+
 function table.key_value_swap(t)
 	local ti = {}
 	for k,v in pairs(t) do
@@ -760,3 +778,28 @@ function core.parse_coordinates(x, y, z, relative_to)
 	local rz = core.parse_relative_number(z, relative_to.z)
 	return rx and ry and rz and { x = rx, y = ry, z = rz }
 end
+
+local function call(class, ...)
+	local obj = core.class(class)
+	if obj.new then
+		obj:new(...)
+	end
+	return obj
+end
+
+function core.class(super)
+	super = super or {}
+	super.__index = super
+	super.__call = call
+
+	return setmetatable({}, super)
+end
+
+function core.is_instance(obj, class)
+	if type(obj) ~= "table" then
+		return false
+	end
+
+	local meta = getmetatable(obj)
+	return meta == class or core.is_instance(meta, class)
+end

builtin/game/init.lua

@@ -2,6 +2,7 @@
 local scriptpath = core.get_builtin_path()
 local commonpath = scriptpath .. "common" .. DIR_DELIM
 local gamepath   = scriptpath .. "game".. DIR_DELIM
+local uipath     = scriptpath .. "ui" .. DIR_DELIM
 
 -- Shared between builtin files, but
 -- not exposed to outer context
@@ -37,6 +38,7 @@ dofile(gamepath .. "forceloading.lua")
 dofile(gamepath .. "statbars.lua")
 dofile(gamepath .. "knockback.lua")
 dofile(gamepath .. "async.lua")
+dofile(uipath .. "init.lua")
 
 core.after(0, builtin_shared.cache_content_ids)
 

builtin/ui/elem.lua

@@ -0,0 +1,100 @@
+--[[
+Minetest
+Copyright (C) 2023 v-rob, Vincent Robinson <[email protected]>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+--]]
+
+ui._elem_types = {}
+
+function ui._new_type(base, type, type_id)
+	local class = core.class(base)
+
+	class._type = type
+	class._type_id = type_id
+
+	ui._elem_types[type] = class
+
+	return class
+end
+
+ui.Elem = ui._new_type(nil, "elem", 0)
+
+function ui.Elem:new(props)
+	self._id = props.id or ui.new_id()
+	self._groups = {}
+	self._boxes = {main = true}
+	self._style = props.style or ui.Style{}
+	self._children = table.merge(props.children or props)
+
+	assert(ui.is_id(self._id), "Element ID must be an ID string")
+
+	for _, group in ipairs(props.groups or {}) do
+		assert(ui.is_id(group), "Element group must be an ID string")
+		self._groups[group] = true
+	end
+end
+
+function ui.Elem:_get_flat()
+	local elems = {self}
+	for _, child in ipairs(self._children) do
+		table.insert_all(elems, child:_get_flat())
+	end
+	return elems
+end
+
+function ui.Elem:_encode()
+	return ui._encode("Bz S", self._type_id, self._id, self:_encode_fields())
+end
+
+function ui.Elem:_encode_fields()
+	local fl = ui._make_flags()
+
+	if ui._shift_flag(fl, #self._children > 0) then
+		local child_ids = {}
+		for i, child in ipairs(self._children) do
+			child_ids[i] = child._id
+		end
+
+		ui._encode_flag(fl, "Z", ui._encode_array("z", child_ids))
+	end
+
+	self:_encode_box(fl, "main")
+
+	return ui._encode("S", ui._encode_flags(fl))
+end
+
+function ui.Elem:_encode_box(fl, name)
+	local box = self._boxes[name]
+
+	-- Element encoding always happens after styles are computed and boxes are
+	-- populated with style indices. So, if this box has any styles applied to
+	-- it, encode the relevant states.
+	if not ui._shift_flag(fl, box.n > 0) then
+		return
+	end
+
+	local box_fl = ui._make_flags()
+
+	-- For each state, check if there is any styling. If there is, add it
+	-- to the box's flags.
+	for i = ui._STATE_NONE, ui._NUM_STATES - 1 do
+		if ui._shift_flag(box_fl, box[i] ~= ui._NO_STYLE) then
+			ui._encode_flag(box_fl, "I", box[i])
+		end
+	end
+
+	ui._encode_flag(fl, "S", ui._encode_flags(box_fl))
+end

builtin/ui/init.lua

@@ -0,0 +1,28 @@
+--[[
+Minetest
+Copyright (C) 2023 v-rob, Vincent Robinson <[email protected]>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+--]]
+
+ui = {}
+
+local UI_PATH = core.get_builtin_path() .. "ui" .. DIR_DELIM
+
+dofile(UI_PATH .. "util.lua")
+dofile(UI_PATH .. "selector.lua")
+dofile(UI_PATH .. "style.lua")
+dofile(UI_PATH .. "elem.lua")
+dofile(UI_PATH .. "window.lua")